1. Field of the Invention
This invention relates to an auxiliary thruster for a maxine vessel and, more particularly, to an auxiliary thruster for a marine vessel that is powered by an integral canned electric motor.
2. Field of the Invention
Marine vessels of all types have utilized auxiliary thrusters to assist in low speed ship maneuvering, station keeping and docking. The most common types of auxiliary thrusters are tunnel thrusters and deployable azimuthing thrusters.
The tunnel thruster is typically a bevel gear driven propeller located in a tunnel extending transversely through the huh of the ship below the water line. The tunnel is typically near the bow or stern of the vessel. When the tunnel thruster is operated, it produces laterally directed thrust in either direction through the tunnel.
Azimuthing thrusters are typically permanently affixed to the hull or deployable out of a cavity in the bottom of the vessel's hull. A conventional azimuthing thruster also uses a gear driven propeller which produces thrust for ship propulsion. The azimuthing thruster can be rotated to direct thrust in any direction for more precise control of the vessel for maneuvering and station keeping. It is desirable that azimuthing thrusters that extend below the hull of the vessel also be retractable into the hull. When the azimuthing thruster extends below the bottom of the vessel, it could be damaged if it strikes the sea bottom when the vessel enters shallow water.
Conventional auxiliary thrusters are powered by electric motors or gasoline or diesel engines. The motor or engine drives the propeller of the thruster through a gear box. This necessitates complex gearing mechanisms for transmitting power from the drive unit to the propeller. In addition, each such auxiliary thruster typically requires its own engine or motor to provide power. When coupled with the space needed for the main power plant for the vessel, space needed for the auxiliary power plants can drastically reduce the amount of usable space in the vessel. There is a need for an auxiliary thruster which can operate as both an azimuthing or tunnel thruster and which is powered by an integral canned electric motor.